Enantioselective Catalytic Diels鈥揂lder Reactions with Enones As Dienophiles

详细信息    查看全文

• 作者：Daniel Carmona ; Fernando Viguri ; Ainara Asenjo ; Fernando J. Lahoz ; Pilar Garc铆a-Ordu帽a ; Luis A. Oro
• 刊名：Organometallics
• 出版年：2012
• 出版时间：June 25, 2012
• 年：2012
• 卷：31
• 期：12
• 页码：4551-4557
• 全文大小：315K
• 年卷期：v.31,no.12(June 25, 2012)
• ISSN：1520-6041

文摘

The aqua complexes (S_M,R_C)-[(畏⁵-C₅Me₅)M(PROPHOS)(H₂O)][SbF₆]₂ [PROPHOS = (R)-propane-1,2-diylbis(diphenylphosphane); M = Rh (1), Ir (2)] are active catalysts for the asymmetric Diels鈥揂lder reaction between ketones and dienes. At low temperatures, enantioselectivities of up to 89% ee are achieved. The intermediate Lewis acid鈥揹ienophile complexes (S_M,R_C)-[(畏⁵-C₅Me₅)M(PROPHOS)(MVK)][SbF₆]₂ (MVK = methyl vinyl ketone; M = Rh (3), Ir (4)) and (S_Ir,R_C)-[(畏⁵-C₅Me₅)Ir(PROPHOS)(EVK)][SbF₆]₂ (EVK = ethyl vinyl ketone (5)) have been isolated and characterized by analytical and spectroscopic means, including the determination of the crystal structure of the iridium complexes 4 and 5 by X-ray diffractometric methods. Structural parameters indicate that the dispositions of the coordinated dienophiles are controlled by the CH/蟺 attractive interactions established between a phenyl group of the PROPHOS ligand and the 伪-vinyl proton of the ketones. Proton NMR parameters indicate that these interactions are maintained in solution. From these data, the stereoselectivity of the catalytic reaction is discussed.